For example, a welded structure is disclosed in the following Patent Literature 1. This welded structure is a steam generator in a nuclear power plant. This steam generator has a channel head and a partition plate for partitioning an inside of the channel head. The channel head includes a base material formed of low-alloy steel and a cladding (welding material) formed by performing built-up welding of austenitic stainless on a surface of the base material. The partition plate is formed of a nickel-based alloy. This partition plate is welded to the surface of the channel head, that is, the surface of the cladding formed of the austenitic stainless.